An Exploratory Study of the Effect of the Atazanavir (ATV) I50L Mutation on Subsequent Treatment Response

This study will compare the response of subjects who failed a first-line ATV-containing regimen and who have the 150L-containing virus to subsequent protease inhibitor (PI)-containing therapy with that of a cohort who has failed a first-line reverse transcriptase inhibitor (NNRTI), and is subsequently receiving PI-containing therapy.